The subject invention relates generally to pipe fittings used to transport abrasive materials such as coal, ash, etc. in connection with industrial applications and, more particularly, to a pipe elbow having an inner lining which is highly resistant to abrasive wear from the material transported through it.
In conveying abrasive materials such as, for example, coal in a slurry, curved sections of pipe must be made of a highly durable material in order to withstand abrasive contact with the material being conveyed therethrough. For this purpose, it is a well known practice to provide pipe elbows with an abrasion resistant inner lining to increase the wear life of the pipe elbow. Due to their excellent wear characteristics, ceramic materials have become increasingly popular for use in lining pipe casings subjected to high abrasive wear conditions.
One known method for providing a ceramic inner wear liner for a pipe fitting involves bricking the inner surface of the pipe elbow casing with a plurality of ceramic wear bricks. The wear bricks are fitted into position inside the casing in a series of rings in a keystone arrangement along the length of the elbow. Unfortunately, it is extremely expensive to provide a ceramic inner lining for a pipe elbow in this fashion because each brick is differently sized and shaped according to its angular location about the center line of the pipe elbow. Nevertheless, the use of ceramic wear bricks to totally line the inner surface of a pipe elbow results in a pipe elbow having an extremely long wear life.
Another method for providing a ceramic inner lining involves pouring a castable ceramic material inside the casing of the pipe elbow in the space between the casing and a sacrificial liner. The inner disposed sacrificial liner is constructed to wear away very quickly in use, thereupon exposing the wear resistant castable ceramic. Unfortunately, while a castable ceramic liner is much cheaper to construct than a wear liner composed of ceramic wear bricks, castable ceramic liners are not nearly as resistant to wear.
An inherent disadvantage in the construction of many pipe elbows having wear resistant inner liners is that once they have worn through they are often not repairable. This is unfortunate because frequently only a portion of the wear liner along the outside center line of the pipe elbow has experienced substantial wear. Since it is very expensive to replace an entire pipe elbow, it would be a significant cost savings to replace only the worn out sections of the elbow so as to render it useful for further service. Optimally, the pipe elbow should be constructed so as to permit repairs to be made on-site without having to remove the elbow from adjacent pipe fittings and lengthening system down time.
The following patent reference are believed to be generally pertinent to the present invention:
______________________________________ Patent No. Inventor ______________________________________ 3,794,359 Fisher 4,130,300 Sheridan 785,176 Mommertz 4,199,010 McGuth et al. 4,478,253 Everett 4,251,170 Sheridan 1,518,705 Raun ______________________________________
U.S. Pat. No. 3,794,359 to Fisher discloses a pipe fitting having an inner wear resistant lining comprised of a series of part circular ceramic wear plates and a grout material comprising a mixture of thermosetting resin and metal coated ceramic particles. The ceramic wear plates are disposed along the portion of the pipe elbow subjected to greatest wear.
U.S. Pat. No. 4,478,253 to Everett discloses an erosion resistant pipe elbow comprising a metal outer casing and an inner castable ceramic material.
U.S. Pat. No. 4,251,170 to Sheridan discloses a ceramic wear liner for small pipe lines having an inside diameter of 2"-8". The pipe liner is disposed on the outside of the pipe casing along the outer bend of the elbow.
U.S. Pat. No. 4,130,300 to Sheridan discloses a composite abrasion resistant pipe elbow having a wear resistant liner composed of a plurality of ceramic wear blocks disposed about the outside bend portion of the pipe elbow. The pipe elbow has a removable cover plate for inspection and replacement of the wear blocks if they are excessively worn. Only a portion of the inner circumference of the pipe elbow is provided with a wear resistant inner lining and there is no way to monitor the degree to which the blocks have been worn other than by necessitating a system shutdown.
U.S. Pat. No. 785,176 to Mommertz discloses an abrasion resistant pipe liner for straight sections of pipe.
U.S. Pat. No. 1,518,705 to Raun discloses a pipe elbow provided with corrugations along the inner portion of the elbow which is subjected to abrasive contact by pieces of material flowing therethrough. The corrugations provide a wearing surface for the pieces of material to ride upon.
U.S. Pat. No. 4,199,010 to McGuth, et al. discloses a pipe elbow having a circular casted ceramic inner liner within an outer metallic casing.